On a more serious note, the open web was killed when people decided to use the browser as an application platform instead of as a document delivery platform.
The open web was killed by many things:
- minification
- node_modules
- webpack
- wasm
- react
Painting on a canvas is the proper way to render application UI.
You can screenscrape HTML based web apps and there are numerous applications enabled by this - from in-browser extensions (eg grammerly) to the ability of Excel to import tables from the web. DOM-based pages is an imperfect model but it has enabled vast extensionability.